How boat insurance works?

Most marinas will require some amount of liability coverage which is easy and cheap enough to get. Hull coverage in any amount is much harder and comes with significantly higher premiums.

Talk to some insurers befor buying the boat.
Most have limits on age of vessel, construction types they will and wont cover, most demand full out of water survey before going on risk and then at certain intervals, normally every 3 years.
They have conditions on where the boat is kept, used, and distance from shore . All these things are negotiable but impact the price, deductable and terms.
Also if you are living on it that adds a whole different complication to a recreational boat policy.
Call them , discuss the boat you are looking at, discuss your planned use, and see what they offer, before you comit to buying

Never say your a live aboard! Your a Cruiser between planned voyages doing a refit and provisioning!